Sho Fukamachi was an ordinary high-school student with no real worries beyond moving along in school and trying to catch the eye of Mizuki Segawa, the younger sister of his best friend, Tetsuro Segawa. That is, until he witnessed an explosion on a nearby mountain and came across a mysterious artifact which granted him the power to summon a suit of Bio-Boosted Armor called the Guyver. An evil corporation, Chronos, lost that Guyver unit in the explosion that Sho witnessed, and will go to any lengths, using any underhanded measures, to get it back. Using their army of modified humans (called Zoanoids, capable of transforming into monstrous forms with increased speed and strength, and occasionally other enhancements), and even the second Guyver unit still in their possession, Chronos attempts to regain possession of the Guyver which has bonded itself to Sho.